291 results about "Turbo decoder" patented technology

A bandwidth efficient advanced modulation waveform modem using concatenated iterative turbo coding and continuous phase modulation is disclosed. A demodulator in the modem has a turbo decoder and a decision feedback carrier and time tracking algorithm to track a carrier and adjust timing. The decision feedback carrier and time tracking algorithm may use an APP decoder as a decision device to provide symbol decisions at a high error rate and low latency for a coded input data stream. A symbol phase estimator produces a symbol phase error estimate from the symbol decisions. An erasure decision function decides which symbol decisions are correct and which symbol decisions are erasures. A carrier tracking function receives the symbol phase error estimates when the symbol decisions are correct and receives erasure inputs when the symbol decisions are erasures to maintain carrier tracking.

A linear turbo-equalizer for use in a CDMA receiver equalizes a despread received signal (rather than the spread received signal) to suppress self-interference resulting from coupling between transmitted symbols. In an example implementation, a linear equalizer based on a generalized-Rake (G-Rake) receiver design uses decoder feedback in forming Rake combining weights as well as in forming a self-interference estimate removed from the equalizer signal provided to the decoder. Preferably, turbo de-coding is also performed. In that case, each turbo-decoder component preferably executes one pass before feeding back information to the equalizer. This ensures that the turbo-decoder does not prematurely lock onto an incorrect code word before feeding back extrinsic information to the equalizer.

Disclosed is a method and communication device for suppressing interference. The method comprises performing, with a turbo decoder (314), at least one turbo decoding attempt (1106) on a received signal (1104). The turbo decoding attempt generates at least one whole word code bit therefrom (1108). The whole word code bit (1108) corresponds to a group of bits comprising a transmitted symbol. The method determines if the whole word code bit (1108) has a confidence level exceeding a given threshold (1110). If the whole word code bit (1108) does have a confidence level exceeding the given threshold, the whole code word bit is selected for use in data symbol recovery (1114).

System and method of estimating radio channel bit error rate (BER) in a digital radio telecommunications system wherein the soft output of the turbo decoder is used as pointer or index to look-up-tables containing the bit-wise BER of a certain bit in the data field of the received frame. A quantizer quantizes the received data frame and the quantized bit operates on a switch which selects the appropriate look-up-table. By means of accumulation and scaling the average BER of a certain amount of bits are calculated. Decoding bit-errors may occur but as they are submitted to posterior probability estimation, systematic errors which normally happen at low SNR are avoided.

A pre-decoder applied to a turbo decoder for decoding a punctured turbo code. The turbo code consists of a data bit stream and a plurality of parity bit streams, parts of which are punctured. The pre-decoder has an arithmetic unit for calculating estimated parity bit streams by carrying out, with respect to the data bit stream, the same algorithm used by a turbo encoder to produce the parity bit streams, a comparison unit for comparing the plurality of parity bit streams with the estimated parity bit streams, and a recovery unit for substituting estimated parity symbols for corresponding punctured parts of the parity symbol streams when related non-punctured bits of the parity bit streams are identical with corresponding estimated non-punctured parity bits. The punctured parity symbols are recovered by the pre-decoder completely, or at least partially, and provided to the turbo decoder. Accordingly, the decoding performance of the turbo decoder is enhanced.

A decoding apparatus and decoding method for performing iteration decoding the suitable number of iterations, and thereby securing the desired transmission quality while decreasing the processing delay. Turbo decoder 301 iterates error correcting decoding on input coded sequences. Error checker 302 decodes an error detecting code contained in a decoded result of the error correcting decoding, and checks whether or not an error remains in the decoded result in turbo decoder 301. Iteration controller 303 instructs turbo decoder 301 to continue the iteration decoding until the number of iterations in the iteration decoding is more than or equal to the constraint number of iterations and error checker 302 determines no error in the decoded result.

In iterative-diversity (ID) transmission systems for signals with concatenated convolutional coding (CCC), paired iterative diversity signals each have ½ the code rate of the 8VSB DTV signals prescribed by the 1995 ATSC Digital Television Broadcast Standard. Known serial concatenated convolutional coding (SCCC) or novel parallel concatenated convolutional coding (PCCC) is used in such system. Pairs of CCC signals code data bits and ones' complemented data bits respectively, using similar coding algorithms. Receivers for this transmission system use respective turbo decoders for turbo decoding the earlier-transmitted and later-transmitted CCC signals. Turbo decoding of the earlier-transmitted portions of iterative diversity signals is delayed to be contemporaneous with turbo decoding of the later-transmitted portions of iterative diversity signals. This facilitates the turbo decoders exchanging information concerning confidence levels of data bits during the turbo decoding procedures.

Disclosed is an apparatus for stopping iterative decoding in a turbo decoder performing iterative decoding on a received frame comprised of information bits and then outputting the iteratively decoded results. A turbo decoder sequentially outputs absolute LLR (Log Likelihood Ratio) values associated with the respective information bits of the received frame by the iterative decoding, and stops the iterative decoding in response to a stop command for the iterative decoding. A minimum LLR detector selects a minimum value M(i) among the sequentially output absolute LLR values. A controller issues a command to stop the iterative decoding, if the minimum value M(i) is larger than a first threshold determined based on a minimum value Fmin among absolute LLR values output through previous iterative decoding.

A bit scrambling method and apparatus for packet transmission / reception in a wireless communication system are provided. A transmitter performs bit scrambling before CRC attachment and a receiver performs bit descrambling after a CRC check. This enables termination of iterative decoding at a turbo decoder according to the CRC check. Hence, power consumption is reduced and throughput is increased at a receiver.

A multi-user turbo decoder combining multi-user detection and forward error correction decoding is disclosed that utilizes iterative decoding of received, interfering signals, and the construction of a decoding tree of the decoder is changed for each iteration of the decoding based on the previous conditional probability estimates of the value of the data bits of each signal making up the received, interfering signals. Before each iteration of multi-user decoding, a probability estimate is calculated that the value of the bit in a signal has a certain value for all of the data bits. Using the probability estimate a new decoding tree is constructed before each iteration of decoding such that the signal bit having the most reliable estimate is assigned to the lowest or root level of the tree. Using the probability estimate for the other signal bits, the signal bit having the next most reliable estimate is assigned to the second level of the tree, and so forth, with the signal bit having the least reliable estimate being assigned to the highest level of the tree adjacent the terminating nodes or leaves of the tree. By building the decoding tree in this manner for each iteration of symbol decoding, a reduced complexity search is more likely to include paths (and nodes) in the tree containing the correct value for the channel symbols.

A processor on which software interleaver is run is provided. The interleaver generation is split into two parts to reduce the overhead time of interleaver changing. First preprocessing prepares seed variables requiring a small memory. Second on-the-fly address generation generates interleaved address through simple adding and subtracting operations using the seed variables.

An apparatus for controlling a Hybrid Automatic Repeat Request (HARQ) is provided. In the apparatus, a physical layer includes a decoder for decoding a control message received over the packet data control channel, a demodulator for demodulating packet data received over the packet data channel, and a turbo decoder for decoding the demodulated packet data. A physical layer's HARQ controller determines whether to demodulate and decode the received packet data depending on a decoding result of the control message, outputs the decoded control message to the demodulator and the turbo decoder for demodulation and decoding of the received packet data, controls output of a response signal according to decoding result of the packet data, and delivers the turbo-decoded packet data to an upper layer.

Methods of early-termination and output selection for iterative decoders are disclosed. A hybrid early-termination method combines the output-comparison-based method with the parity-check-based method. The hybrid approach is far more superior in termination reliability in either of the two individual approaches, without their disadvantages. The hybrid termination method effectively and reliably terminates the iterative decoding process, cutting the majority of the computational load while eliminating the degradation in the bit error rate (BER) and frame-error-rate (FER) performance due to incorrectly terminated frames. An output selection procedure chooses the best possible decoded frame among those from all iterations if the iterative decoding process cannot be early-terminated during the decoding of a received frame and if the iterative decoder has reached the maximum number of iterations, thereby eliminating the iteration abnormality that is inherent in the iterative decoding approach, and improving the BER performance of the standard iterative decoders.

An efficient turbo decoder. The disclosed turbo decoder includes a first mode of operation in which the turbo decoder uses a first functional loop. The first functional loop includes a memory bank, a read interleaver, a first multiplexer (MUX), a RAM file, a log-MAP decoder, a write interleaver, and a second MUX. The disclosed turbo decoder further includes a second mode of operation in which a second functional loop is used. The second functional loop includes the memory bank, the first MUX, the RAM file, the log-MAP decoder, and the second MUX. The memory bank is a dual port extrinsic memory. The disclosed turbo decoder circuit switches between the first mode and the second mode.

Detection of errors in the results of turbo decoding is performed while decoding is being repeated. If absence of errors is detected, the results of decoding are output, even though repetition of the decoding operation is in progress, and further decoding is discontinued. Further, the number of times errors are detected in decoded results when decoding has been performed a set number of times is monitored and the decoding operation is executed again if the number of times errors are detected is equal to or less than a set value. Further, one of first and second decoded results output from first and second elementary decoders that construct a turbo decoder is selected as appropriate and is then output.

An iterative forward error control code (FECC) decoder (28; 28′) is disclosed. The decoder (28; 28′) operates by adjusting probability values for codeword bits at a selected iteration in the decoding sequence. According to one disclosed embodiment, those probability values that are above a certain threshold value prior to one of the last decoding iterations are adjusted to a full reliability value. According to other disclosed embodiments, a linear or non-linear adjustment function is applied. The decoder may be a turbo decoder, a Low Density Parity Check (LDPC) decoder, or a decoder for any FECC code for which iterative decoding is appropriate.

This disclosure relates to providing negative stopping criteria for turbo decoding for a wireless device. A device may wirelessly receive turbo coded data. Turbo decoding may be performed on the turbo coded data. Performing turbo decoding may use one or more negative stopping criteria for early termination of the turbo decoding for each code block of the turbo coded data. The negative stopping criteria may be selected to terminate the turbo decoding of a code block early under poor wireless medium conditions. Turbo decoding of a code block may be terminated early if the one or more negative stopping criteria for the code block are met.

A transmitting system, a receiving system, and a method for processing a broadcast signal are disclosed. The receiving system comprises a tuner, a channel equalizer, a turbo decoder, a demultiplexer, a first error correction decoder, a block deinterleaver, and a second error correction decoder. The tuner receives a broadcast signal including a data group. The data group comprises mobile service data, regularly spaced known data sequences, and signaling data. The turbo decoder performs turbo decoding for the signaling data included in the channel equalized broadcast signal in the channel equalizer. The block deinterleaver performs block deinterleaving for the turbo-decoded FIC data in a block unit of TNoG (the number of all data groups assigned to one subframe)×51 bytes.

A signal-to-noise estimator is provided for estimating the signal-to-noise ratio in wireless fading channels. The estimator can be applied to likelihood ratio estimation of turbo decoders in third generation wide-band code division multiple access (WCDMA) systems. Time-multiplexed samples of pilot symbols from a wireless receiver are supplied to the estimator to obtain individual estimates of signal power and / or noise power. The estimator uses a de-correlating filter in which the coefficients are known functions (such as eigen-vectors) of the auto-correlation matrix for a wireless channel. The decorrelating filter is used by the estimator to map an observation vector into a set of statistically independent samples. The energy of each vector component is computed individually and combined to produce an aggregate sum for the vector. The aggregate sum can be subtracted from the pilot tone power in order to produce an estimate of noise power.

A stopping criterion improvement for a turbo decoder that does not require division by a variable quantity. The stopping criterion improved upon generates a signal-to-noise ratio based on the mean and variance of soft-output estimates. The decoding process is aborted based on a comparison of the generated signal-to-noise ratio to a predetermined threshold.

In a method for transmitting data in a digital transmission system given packet-switched service, for purposes of channel coding, a turbo-coding is performed in a turbo-coder at the sender side and a turbo-decoding with soft decision output signals is performed in a turbo-decoder at the receiver side. To trigger an ARQ, the channel quality is estimated by a parameter estimation method; the variances of the soft decision output signals at the turbo-decoder are determined; the correctness or respectively, defectiveness of the transmitted packet is inferred from the channel quality and the variances; and a retransmission of at least a part of defective packet is triggered. In the retransmission of the information of a defective packet, at least part of the information suppressed by the dotting in the precious transmission is sent. This additional information is [. . .] inserted into the already existing information at the receiver side, and this complete information is decoded again.

Removing adverse effects in case error detection using error detection codes cannot be performed correctly, and improving the data transmission efficiency. The turbo decoder 6 compares data which is decoded this time with data which is decoded previous time, both of which are decoded in repetitive decoding processing, to obtain discord number information indicative of the number of discordant sign bits, and sends the information to a terminal I / F unit 7 and a packet flow retransmission controlling unit 10. Even though it is determined that error detection result from a CRC recalculating unit 9 shows that there exists no bit error, in case the number of discordant sign bits is larger than a predetermined threshold value, it is determined that there is generated error. And, a packet flow retransmission controlling unit 10 sends a signal requesting retransmission of data. Furthermore, data amount to be retransmitted is varied in accordance with the number of discordant sign bits to improve the data transmission efficiency.

A method and apparatus for controlling iterative decoding in a turbo decoder are provided, in which a maximum number of iterations is determined for current data to be decoded based on at least one of current HARQ information necessary for a HARQ operation of the current data, previous HARQ information about previous data, and early stop information indicating whether iterative decoding of the previous data was early stopped. A turbo decoder iteratively decodes the current data within the maximum number of iterations.